Vacuum polarization of Dirac fermions in the cosmological de Sitter global monopole spacetime

Abstract

We study the vacuum polarization effects of the Dirac fermionic field induced by a pointlike global monopole located in the cosmological de Sitter spacetime. First we derive the four orthonormal Dirac modes in this background in a closed form. Quantizing the field using these modes, we then compute the fermionic condensate, $⟨0|\overline{\mathrm{\ensuremath{\Psi}}}\mathrm{\ensuremath{\Psi}}|0⟩$, as well as the vacuum expectation value of the energy-momentum tensor for a massive Dirac field, regularized in a particular way. We have used the Abel-Plana summation formula in order to extract the global monopole contribution to these quantities and have investigated their variations numerically with respect to relevant parameters.